We have developed a model of the human blood-brain barrier (BBB) using autologous endothelial cells (EC) and astrocytes obtained from human fetuses. This model system has provided information about the functioning of the BBB during inflammatory conditions. It has also permitted the development of new hypotheses about how BBB EC may play a pivotal role in the pathogenesis of HIV CNS disease. Our focus is on the expression of EC adhesion molecules and the role of cytokines in this process. An understanding of these issues will provide information about the underlying pathologic mechanisms of CNS disease during HIV infection and may present a strategy to interrupt the process. The specific hypothesis to be tested in this proposal is that adhesion molecule expression by BBB EC facilitates the binding, and subsequent extravasation into the CNS parenchyma, of HIV-infected cells. Additionally, the adhesion of infected cells to the vasculature may result in EC infection. The role of adhesion molecules expressed by EC during inflammatory conditions is now recognized. Also, a role for adhesion molecules expressed by EC in the pathogenesis of AIDS has been suggested. However, the definition of a role for adhesion molecules in CNS disease during fetal HIV infection and pediatric AIDS remains to be established. This proposal is designed to investigate our hypothesis by using cell and molecular biologic techniques combined with microscopy and immunocytochemistry. The following studies will be conducted: 1) to characterize further this model of the BBB with respect to its structural properties, adhesion molecule expression, and the role of cytokines and HIV as inducers of adhesion molecules; 2) to determine whether the adhesion molecules under study in the BBB model system are expressed in vivo 3) to determine the mechanisms of binding and transmigration of HIV-infected and noninfected mononuclear cells through the BBB using this model, 4) to determine whether EC, cocultured with autologous astrocytes, can be infected with cell-associated virus; 5) to examine the effect of HIV, either cell-associated or cell-free, on the structure and function of EC in this co-culture model; and, 6) to examine the induction of cytokine expression by cells of this model in response to exogenous cytokines, HIV-infected mononuclear cells or cell-free virus.